WO2019234831A1

WO2019234831A1 - Endoscope system

Info

Publication number: WO2019234831A1
Application number: PCT/JP2018/021597
Authority: WO
Inventors: 翔進士
Original assignee: オリンパス株式会社
Priority date: 2018-06-05
Filing date: 2018-06-05
Publication date: 2019-12-12
Also published as: JP7093409B2; US11805988B2; CN112203572B; JPWO2019234831A1; US20210106215A1; CN112203572A

Abstract

This endoscope system (1) is provided with: an illumination unit (4) for irradiating an object (A) with illumination light (L) having an intensity distribution which has bright portions and dark portions spatially repeated in a luminous flux cross section; an intensity distribution change unit (5) for changing the width of the dark portions; an imaging unit (6) for acquiring a plurality of illumination images of the object (A) irradiated with illumination light beams (L) having mutually different dark portion widths; a separation processing unit (7) for generating a first separated image and a second separated image from each illumination image, the first separated image including more information of a deeper layer of the object (A) than the second separated image; and a computation unit (8) for calculating depth information of a feature part within the object (A) on the basis of a change among the first separated images and a change among the second separated images.

Description

Endoscope system

The present invention relates to an endoscope system.

2. Description of the Related Art Conventionally, an endoscope system that calculates the thickness and depth of a blood vessel within an observation range using a ratio of image signals in three wavelength bands having different light absorption characteristics of hemoglobin has been proposed (for example, patents). Reference 1).

JP 2016-174836 A

知る When a lesion is detected by endoscopy, it is important to determine how deeply the lesion has reached to determine the subsequent response. Since the technique of Patent Document 1 uses the light absorption characteristics of hemoglobin, the tissue whose depth can be calculated is limited to blood vessels. That is, there is a problem that the depth of a lesioned part that does not change blood vessels compared to a normal part and a lesioned part that does not include a blood vessel cannot be calculated by the technique of Patent Document 1.

The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide an endoscope system that can acquire depth information of a feature portion in a subject regardless of the absorption characteristics of the feature portion. And

In order to achieve the above object, the present invention provides the following means.
One embodiment of the present invention irradiates a subject with illumination light, and the illumination light has an intensity distribution in which a bright portion and a dark portion are spatially repeated in a light beam cross section perpendicular to an optical axis, and the illumination light An intensity distribution changing unit that changes a width of the dark part in the intensity distribution; an imaging unit that acquires a plurality of illumination images of the subject that are illuminated with illumination lights having different widths of the dark part; A separation processing unit that creates a first separated image and a second separated image from each of the illumination images, and wherein the first separated image includes more information about the depth of the subject than the second separated image; A calculation unit that calculates depth information of the feature in the subject based on the plurality of first separated images and the plurality of second separated images created from the plurality of illumination images, A separation processing unit Based on at least two intensity values among the intensity values of the pixels in the illumination image corresponding to each of the writing part, the dark part, and the part having the intensity between the bright part and the dark part, the first And a second separated image, and the arithmetic unit calculates depth information of the feature based on a change between the plurality of first separated images and a change between the plurality of second separated images. This is an endoscope system.

According to one embodiment of the present invention, when illumination light is irradiated onto a subject that is a scatterer, specular reflected light (specular light) that is specularly reflected on the surface of the subject and scattering on a surface layer inside the subject. Surface scattered light emitted from the surface of the subject and internal scattered light emitted from the surface of the subject through scattering in the deep layer inside the subject are generated. By irradiating the subject with illumination light having a spatially non-uniform intensity distribution from the illumination unit, the internal scattered light is spatially separated from the specular light and the surface scattered light. That is, specular light, surface scattered light, and internal scattered light are generated in the bright part, whereas internal scattered light that circulates from the bright part to the dark part is predominantly generated in the dark part.

Therefore, the region corresponding to the dark portion in the illumination image acquired by the imaging unit includes a lot of deep layer information, and the region corresponding to the bright portion includes a lot of surface and surface layer information. Information means the amount of light that is incident on a living tissue and is emitted from the living tissue after being subjected to modulation such as scattering or absorption by the living tissue or a structure inside the living tissue. The separation processing unit includes a lot of information of different depths based on at least two intensity values among the intensity values of pixels corresponding to each of the bright part, the dark part, and the part having the intensity between the bright part and the dark part. First and second separated images can be created.

Specifically, the separation processing unit can create a first separated image (deep layer image) including a lot of information on the depth of the subject based on the intensity value of the pixel in the region corresponding to the dark part.
Further, the separation processing unit can create a second separated image (surface layer image) including a lot of information on the surface and surface layer of the subject based on the intensity value of the pixel in the region corresponding to the bright part. Alternatively, the separation processing unit performs the second separation including a lot of information on a position shallower than the deep layer and deeper than the surface layer based on the intensity value of the pixel in the region corresponding to the portion having the intensity value between the bright part and the dark part. Images can be created.

In this case, the width of the dark part of the illumination light applied to the subject is changed by the intensity distribution changing unit, and a plurality of illumination images of the subject illuminated with illumination light having different dark part widths are acquired by the imaging unit. Is done. The separation depth between the first and second separated images becomes deeper as the width of the dark part in the subject is larger. The separation depth is a rough boundary between the depths of information included in the first and second separated images. That is, the first separated image mainly includes information on a layer deeper than the separation depth, and the second separated image mainly includes information on a layer shallower than the separation depth. The smaller the dark part width, the shallower the first separated image, and the larger the dark part width, the deeper the second separated image. Therefore, the depth information of the feature portion in the subject can be acquired based on the change of the plurality of first separated images and the change of the second separated image created from the plurality of illumination images. Further, by using the illumination image based on the scattered light from the feature portion, the depth information of the feature portion can be acquired regardless of the absorption characteristics of the feature portion.

In the above aspect, the illuminating unit emits the illumination light so that a pattern of the bright part and the dark part on the subject is enlarged in proportion to a shooting distance between the imaging unit and the subject. It may be emitted as a divergent light beam.
With this configuration, it is possible to change the width of the dark portion on the subject simply by changing the shooting distance.

In the above aspect, the imaging apparatus includes a shooting distance measuring unit that measures a shooting distance between the imaging unit and the subject, and the intensity distribution changing unit is configured such that the intensity distribution of the illumination light on the subject is the imaging unit. The period between the bright part and the dark part in the intensity distribution may be changed based on the photographing distance so as to be constant regardless of the distance to the subject.
With this configuration, the relationship between the dark part width on the illumination part and the dark part width on the subject can be made constant regardless of the shooting distance.

In the above aspect, the illumination light includes a plurality of lights having different wavelengths, and the plurality of lights has the intensity distribution in which a period between the bright part and the dark part decreases as the wavelength increases. It may be.
Since the light that has entered the subject reaches a deeper position as the wavelength is longer, the internally scattered light of the light having a longer wavelength includes deeper layer information. The longer the wavelength, the smaller the period between the bright part and the dark part, thereby reducing the difference in information depth due to the difference in wavelength.

In the above aspect, the intensity distribution of the illumination light may have a striped shape in which the band-like bright portions and the dark portions are alternately repeated in the width direction.
With this configuration, it is possible to effectively separate the internally scattered light with a simple light and dark pattern. In order to create the first and second separated images with high resolution, two or more illumination images of a subject illuminated with illumination light having different positions of the bright part and the dark part are used. By changing the intensity distribution only in the width direction of the stripe, the positions of the bright part and the dark part can be easily changed over time.

In the above aspect, the intensity profile in the width direction of the bright part and the dark part of the intensity distribution of the illumination light may be substantially sinusoidal.
By irradiating the subject with illumination light whose intensity varies spatially in a sine wave shape, the intensity value for the second separated image when the highest intensity light is applied and the light with the lowest intensity are applied. The intensity value for the first separated image can be calculated by the phase shift method. Thereby, the 1st and 2nd separated image with high resolution can be created from a small number of illumination images.

In the aspect described above, a polarization control unit that controls a polarization state of the illumination light and a polarization selection unit that selects a polarization state of light incident on the imaging unit from the subject.
When the subject is irradiated with illumination light, specular reflection light (specular light) can also be generated in addition to the surface scattering light and the internal scattering light. The specular light is specularly reflected on the surface of the subject and is included in the second separated image. Specular light has the same polarization state as illumination light, whereas surface scattered light and internally scattered light do not have a specific polarization state. Therefore, by selectively allowing light other than specular light to enter the imaging unit by the polarization selection unit, it is possible to create a second separated image that does not include specular light. Then, based on the second separated image that does not include specular light, more accurate depth information of the feature portion can be acquired.

In the above aspect, the calculation unit is characterized in that the feature is based on a correspondence table in which a width of the dark part and a separation depth between the first separated image and the second separated image are associated with each other. The depth information of the part may be calculated.
With this configuration, it is possible to know from what separation depth each layered image contains information about the layer depth from the separation depth associated with the width of the dark part in the correspondence table. Therefore, the depth information of the feature portion can be easily calculated by acquiring the separation depth of the separated image including the feature portion from the correspondence table.

In the above aspect, the calculation unit calculates the contrast of each of the plurality of sets of first and second separated images, and calculates the depth information of the feature unit based on the contrast and the correspondence table. Also good.
The contrast of the separated image including the feature part is higher than the contrast of the separated image not including the feature part. Therefore, it is possible to easily specify the separated image including the feature portion based on the contrast. Then, by obtaining the separation depth associated with the width of the dark part of the identified separated image from the correspondence table, the depth information of the feature part can be calculated.

According to the present invention, it is possible to obtain the depth information of the characteristic part in the subject regardless of the absorption characteristic of the characteristic part.

1 is an overall configuration diagram of an endoscope system according to an embodiment of the present invention. It is a figure which shows an example of the time change of the light-dark pattern of illumination light. It is a figure explaining the production method of the surface layer image and deep layer image by a separation process part. It is a figure explaining the relationship between the width | variety of the dark part of illumination light, and the separation depth. It is a figure explaining the relationship between the width | variety of the dark part of illumination light, and the separation depth. It is a figure which shows the relationship between the pitch of the brightness-and-darkness pattern of the illumination light irradiated to a biological tissue, and a separation depth. It is a figure which shows the surface layer image and deep layer image of the biological tissue of FIG. 5A, and is a figure explaining the relationship between the separation depth and the contrast of a surface layer image and a deep layer image. It is a graph which shows the relationship between a separation depth and the contrast of a surface layer image and a deep layer image. It is a graph which shows the relationship between the pitch of the brightness-and-darkness pattern of illumination light, and the contrast of a surface layer image and a deep layer image. It is a graph which shows the relationship between the pitch of the light / dark pattern of illumination light, and the separation depth. It is a flowchart which shows operation | movement of the endoscope system of FIG. It is a figure which shows the other structural example of an illumination part and an intensity distribution change part. It is a figure explaining the light-dark pattern of the illumination light produced | generated by the illumination part of FIG. 10A, and its time change. It is a figure which shows the other structural example of an illumination part and an intensity distribution change part. It is a figure explaining the other example of the time change of the intensity distribution of illumination light. It is a figure which shows the space profile of the intensity | strength of the illumination light in the II line | wire of FIG. 11A. It is a fragmentary block diagram of the modification of an endoscope system provided with a polarization control part and a polarization selection part.

Hereinafter, an endoscope system 1 according to an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the endoscope system 1 according to the present embodiment includes an endoscope 2 that observes the inside of the body, and a main body 3 that is connected to the proximal end of the endoscope 2.
In addition, the endoscope system 1 includes an illuminating unit 4 that illuminates a living tissue (subject) A in the body with illumination light L having a bright and dark pattern, an intensity distribution changing unit 5 that changes a light and dark pattern of the illumination light L, and illumination. An imaging unit 6 that acquires an illumination image of the living tissue A illuminated with the light L, and a separation processing unit 7 that creates a surface layer image (second separated image) and a deep layer image (first separated image) from the illuminated image. And a calculation unit 8 that calculates information on the depth of the characteristic portion E (see FIG. 5A) in the living tissue A based on the surface layer image and the deep layer image. The feature E is a tissue existing in the living tissue A, and is, for example, a blood vessel or a lesion.

The illumination unit 4 generates illumination light L having a spatially non-uniform intensity distribution in a light beam cross section perpendicular to the optical axis, and emits the illumination light L from the distal end of the endoscope 2 toward the living tissue A. . The illumination light L is, for example, single wavelength light such as white light and infrared light, single color light such as red, green, and blue, or mixed light of a plurality of lights having different wavelengths. The illumination light L generally has an intensity gradient in which the brightness gradually decreases from the center of the light beam toward the periphery. Apart from the overall intensity gradient of the light beam cross section, the illumination light L has a light and dark pattern in which a high intensity bright part and a dark part having a lower intensity than the bright part are alternately repeated in the light beam cross section. As shown in FIG. 2, the light / dark pattern is a stripe pattern in which straight belt-like bright portions and dark portions are alternately repeated only in the width direction orthogonal to the longitudinal direction of the bright portions and dark portions. In FIG. 2, a white area represents a bright part, and a black area represents a dark part. In the light / dark pattern of FIG. 2, the width of the bright portion and the width of the dark portion are equal to each other, but the width of the bright portion and the width of the dark portion may be different from each other.

The illumination part 4 is provided with the light emission part 4a, the reflector 4b, and the mask 4c which were provided in the main-body part 3, as FIG. 1 shows. The illumination unit 4 includes an image guide fiber 4d and a projection lens 4e provided in the endoscope 2. The light output from the light emitting unit 4a is collected by the reflector 4b and illuminates the mask 4c. The mask 4c has a light-transmitting region that transmits light and a light-blocking region that blocks light, and a projection pattern corresponding to a light and dark pattern is formed from the light-transmitting region and the light-blocking region. When the light passes through the mask 4c, the illumination light L having a bright and dark pattern is generated. The mask 4c is a liquid crystal element that can electrically control the light transmittance at each position in the incident region where light enters. The illumination light L generated by the mask 4c is guided by the image guide fiber 4d while preserving the light / dark pattern, and is emitted from the distal end of the endoscope 2 by the projection lens 4e.

As shown in FIG. 2, the intensity distribution changing unit 5 changes the positions of the bright part and the dark part in the bright and dark pattern and the pitch (period of the bright part and the dark part) P of the bright and dark pattern over time. The width Wd of the dark part changes due to the change of the pitch P (P1, P2, P3).
Specifically, the intensity distribution changing unit 5 temporally changes the light / dark pattern in the width direction of the bright part and the dark part, and exchanges the positions of the bright part and the dark part with each other. In FIG. 2, the horizontal direction represents the flow of time. Thereby, a bright part and a dark part are projected at each position within the irradiation range of the illumination light L on the surface B of the living tissue A. The intensity distribution changing unit 5 changes the positions of the bright part and the dark part with time, then changes the pitch P, and changes the positions of the bright part and the dark part with time again. The intensity distribution changing unit 5 repeats changing the pitch P and changing the positions of the bright part and the dark part.

The intensity distribution changing unit 5 includes a control element that controls the light transmittance at each position in the incident region of the mask 4c. The mask 4c made of a liquid crystal element can form an arbitrary projection pattern, and the arbitrary projection pattern can be freely changed over time. The intensity distribution changing unit 5 changes the pitch P and the width Wd of the illumination light L over time by controlling the light transmittance at each position of the mask 4c according to a preset program.

The imaging unit 6 includes an imaging lens 6a that is provided at the distal end of the endoscope 2 and collects light from the biological tissue A, and an imaging element 6b that captures an image of the biological tissue A formed by the imaging lens 6a. . The illumination image acquired by the image sensor 6b is transmitted from the image sensor 6b to the separation processing unit 7.

Here, the intensity distribution of the illumination light L applied to the living tissue A changes with time by the intensity distribution changing unit 5 as shown in FIG. The imaging device 6b acquires a plurality of sets of first illumination images and second illumination images having different pitches of the light and dark patterns. The first illumination image and the second illumination image are images of the living tissue A that is illuminated with the illumination light L in which the dark part and the bright part are interchanged with each other. Therefore, as shown in FIG. 3, in the first illumination image and the second illumination image, the bright area projection area and the dark area projection area are inverted to each other, and the bright area projection areas and the dark area projection areas are mutually inverted. Are images that complement each other. In the first illumination image and the second illumination image in FIG. 3, a white area represents a bright area projection area, and a black area represents a dark area projection area.
Therefore, the operations of the intensity distribution changing unit 5 and the image sensor 6b are provided in the main body 3 so that the timing of changing the intensity distribution by the intensity distribution changing unit 5 and the timing of photographing by the image sensor 6b are synchronized with each other. It is controlled by a control device (not shown).

As illustrated in FIG. 3, the separation processing unit 7 creates a set of surface layer images and a deep layer image from each set of the first illumination image and the second illumination image. For the pixels at the respective positions of the first and second illumination images, the intensity value Imax when the bright part is projected and the intensity value Imin when the dark part is projected are acquired. The separation processing unit 7 calculates the intensity value Is of each pixel of the surface layer image from the following formula (1), and creates a surface layer image having the intensity value Is. Further, the separation processing unit 7 calculates the intensity value Id of each pixel of the deep image from the following formula (2), and creates a deep image having the intensity value Id.
Is = Imax−Imin (1)
Id = Imin × 2 (2)

When the biological tissue A, which is a scatterer, is irradiated with illumination light L having a bright and dark pattern, specular reflection light (specular light), surface scattered light, and internal scattered light are generated from the biological tissue A.
The specular light is reflected light of the illumination light L specularly reflected by the surface B of the living tissue A, and is generated in the projection area of the bright part.
The surface scattered light is scattered light of the illumination light L that is incident on the living tissue A from the projection area of the bright part, passes through the surface layer C while repeating scattering, and is emitted from the surface B. Most of the surface scattered light is emitted from the projection area of the bright part.
The internal scattered light is scattered light of the illumination light L that is incident on the living tissue A from the projection area of the bright part, passes through the deep layer D while repeating scattering, and is emitted from the surface B. A part of the internal scattered light is emitted from the projection area of the bright part, and the other part is propagated to the projection area of the dark part and is emitted from the projection area of the dark part.

That is, the intensity value Imin of the projection area of the dark part in the first and second illumination images is mainly based on the internal scattered light, and mainly includes information on the deep layer D. Therefore, the deep layer image based on the intensity value Imin is an image mainly including information on the deep layer D. On the other hand, the intensity value Imax of the bright portion projection region in the first and second illumination images is based on specular light, surface scattered light, and internal scattered light, and includes information on the surface B, the surface layer C, and the deep layer D. Therefore, the surface layer image based on the intensity value Is is an image mainly including information on the surface B and the surface layer C from which information on the deep layer D is removed.
The separation processing unit 7 creates a plurality of deep layer images and a plurality of surface layer images from the plurality of sets of first illumination images and second illumination images acquired by the imaging unit 6. The created surface layer image and deep layer image are transmitted to the calculation unit 8.

Here, as shown in FIG. 4A and FIG. 4B, the separation depth between the surface layer image and the deep layer image depends on the width Wd of the dark part on the surface B of the biological tissue A. The separation depth is a rough boundary between the depth of information included in the surface layer image and the depth of information included in the deep layer image. That is, the surface layer image mainly includes layer information from the surface B to the separation depth, and the deep layer image mainly includes layer information deeper than the separation depth. The larger the dark portion width Wd, the deeper the separation depth.

FIG. 5A shows the relationship between the pitch (P1, P2, P3, P4, P5) of the light / dark pattern of the illumination light L and the separation depth (d1, d2, d3, d4, d5) in the living tissue A. Yes. FIG. 5B shows an example of the surface layer image and the deep layer image based on the illumination light L of each pitch P1, P2, P3, P4, P5. As shown in FIG. 5B, the feature E at a position shallower than the separation depth is included in the surface layer image, but is not included in the deep layer image. On the other hand, the feature portion E at a position deeper than the separation depth is included in the deep layer image but is not included in the surface layer image.

The calculation unit 8 receives a plurality of deep layer images and a plurality of surface layer images from the separation processing unit 7, and calculates the contrast of each of the plurality of deep layer images and the plurality of surface layer images. As shown in FIG. 6, the contrast of the surface layer image including the feature portion E is larger than the contrast of the surface layer image not including the feature portion E. Similarly, the contrast of the deep layer image including the feature portion E is larger than the contrast of the deep layer image not including the feature portion E. In FIG. 6, a range surrounded by a broken line indicates a depth range where the characteristic portion E exists. FIG. 7 shows the relationship between the pitch P of the light and dark pattern and the contrast. FIG. 8 shows the relationship between the pitch P of the light and dark pattern and the separation depth. From FIG. 7 and FIG. 8, the relationship between the separation depth and the contrast in FIG. 6 is obtained.

The calculation unit 8 calculates the depth of the edge on the shallow side (surface B side) of the feature E based on the change in contrast of the surface layer image with respect to the separation depth. For example, the contrast changes greatly between the surface layer image having the separation depth d1 that does not include the feature portion E and the surface layer image having the separation depth d2 that includes the feature portion E. The calculation unit 8 calculates that the depth of the end on the shallow side of the feature E is between d1 and d2 based on the large change in contrast.

Further, the calculation unit 8 calculates the depth of the end on the deep side of the feature E based on the change in the contrast of the deep layer image with respect to the separation depth. The contrast changes greatly between the deep layer image having the separation depth d3 including the feature portion E and the deep layer image having the separation depth d4 not including the feature portion E. The computing unit 8 calculates that the depth of the end on the deep side of the feature E is between d3 and d4 based on the large change in contrast.
The depth information of the characteristic part E calculated by the calculation part 8 is displayed on a display device (not shown) connected to the main body part 3, for example.

A storage table (not shown) in the main body 3 may store a correspondence table in which the dark portion width Wd and the separation depth are associated with each other. The calculation unit 8 reads the correspondence table from the storage device, and acquires each deep layer image and the separation depth of each surface layer image from the correspondence table based on the dark portion width Wd. Information on the width Wd of the dark portion of the surface layer image and the deep layer image is transmitted from the control device to the calculation unit 8, for example.

Next, as shown in FIG. 6, the calculation unit 8 creates a graph representing the relationship between the separation depth and the contrast of the surface layer image, and creates a graph representing the relationship between the separation depth and the contrast of the deep layer image. Next, the calculation unit 8 detects the separation depth at which the contrast rapidly increases in the graph of the surface layer image based on the inclination of the graph, and identifies the detected separation depth as the shallow end of the feature E. . In addition, the calculation unit 8 detects the separation depth at which the contrast sharply decreases in the graph of the deep layer image based on the inclination of the graph, and identifies the detected separation depth as the end on the deep side of the feature E.

The calculation unit 8 may calculate the contrast of the entire surface image and the entire deep image, but may calculate the contrast of a part of the surface image and a part of the deep image. In this case, it is preferable that the operator can designate a range for calculating the contrast. For example, the main body 3 includes a graphical user interface (GUI). The surgeon can specify a desired range including the feature portion E using the GUI.

The separation processing unit 7 and the calculation unit 8 are realized as programs executed by a computer, for example. That is, the main body 3 includes a processor such as a central processing unit, a main storage device such as a RAM, and an auxiliary storage device such as a hard disk drive. A program for causing the processor to execute the above-described processing by the separation processing unit 7 and the calculation unit 8 is stored in the auxiliary storage device. The program is loaded from the auxiliary storage device to the main storage device, and the processor executes processing according to the program, whereby the above-described functions of the separation processing unit 7 and the calculation unit 8 are realized.

Next, the operation of the endoscope system 1 configured as described above will be described with reference to FIG.
In order to acquire the depth information of the characteristic portion E in the living tissue A using the endoscope system 1 according to the present embodiment, the endoscope 2 is inserted into the body, and an illumination image of the living tissue A is obtained. get. Specifically, the illumination light L is irradiated from the illumination unit 4 to the living tissue A (step S1). The positions of the bright part and the dark part of the illumination light L change over time by the intensity distribution changing unit 5. Imaging of the living tissue A is executed by the imaging unit 6 at two times when the bright part and the dark part are interchanged, and a set of first illumination image and second illumination image is acquired (step S2). Next, the pitch P of the illumination light L is changed by the intensity distribution changing unit 5 (step S4), and another set of the first illumination image and the second illumination image is acquired by the imaging unit 6 (step S2). Steps S4, S1, and S2 are repeated until the first illumination image and the second illumination image based on the illumination light L of all the preset pitches P are acquired (YES in step S3).

Next, the separation processing unit 7 generates a plurality of sets of surface layer images and deep layer images having different separation depths from the plurality of sets of first illumination images and second illumination images (step S5). Next, the computing unit 8 calculates the contrast of each surface layer image and each deep layer image (step S6). Next, depth information of the feature portion E in the living tissue A is calculated by the calculation unit 8 based on the change in the contrast of the surface layer image with respect to the separation depth and the change in the contrast of the deep layer image with respect to the separation depth.

As described above, according to the present embodiment, a plurality of sets of first illumination images and second illumination images are acquired using illumination light L having different dark portion widths Wd, and the plurality of sets of first illumination images and first illumination images are obtained. A plurality of sets of surface layer images and deep layer images having different separation depths are generated from the two illumination images. Then, there is an advantage that the depth information of the feature portion E in the living tissue A can be calculated based on the contrast of the plurality of surface layer images and the contrast of the plurality of deep layer images. The first and second illumination images are images based on the scattered light of the living tissue A and the feature part E. Therefore, there is an advantage that the depth information of the feature E can be acquired from the first and second illumination images regardless of the absorption characteristics of the feature E.

In order to ensure a good balance between the information amount of the deep layer D in the surface layer image and the information amount of the deep layer D in the deep layer image, the width Wd of the dark part on the surface B of the living tissue A is 0.005 mm or more and 25 mm or less. It is preferable.
When the dark portion width Wd is less than 0.005 mm, the ratio of the internally scattered light that wraps around from the bright portion projection region to the dark portion projection region increases, and as a result, the difference between the intensity value Imax and the intensity value Imin decreases. Thus, information on the surface layer C included in the surface image may be insufficient. On the other hand, when the width Wd of the dark part is larger than 25 mm, the internal scattered light cannot reach the center of the projection area of the dark part, and as a result, the intensity value Imin approaches zero and the deep layer D included in the deep image is included. Information can be lacking.

In the present embodiment, the illumination unit 4 illuminates the living tissue A with the illumination light L having a striped intensity distribution. However, the pattern of the intensity distribution of the illumination light L is not limited to this, and the bright part. Another distribution in which the dark portion and the dark portion are spatially repeated may be used. For example, the intensity distribution of the illumination light L may be a checkered pattern, dots, or random dots.

In the present embodiment, the illumination unit 4 generates the illumination light L having a light / dark pattern by the liquid crystal element 4c, and the intensity distribution changing unit 5 changes the light / dark pattern by controlling the liquid crystal element 4c. The configurations of the illumination unit 4 and the intensity distribution changing unit 5 are not limited to this. 10A to 10C show other configuration examples of the illumination unit 4 and the intensity distribution changing unit 5.

10A uses the light interference fringes as a bright and dark pattern. The illumination unit 4 includes a laser light source 4f and an optical path 4g that branches the light output from the laser light source 4f into two and emits the two lights. The optical path 4g is composed of, for example, an optical fiber. When the two lights emitted from the optical path 4g interfere with each other, an interference fringe having a sinusoidal intensity profile as shown in FIG. 10B is generated as a light-dark pattern.

The intensity distribution changing unit 5 in FIG. 10A changes the optical path length of one of the two branched lights, thereby causing the position of the interference fringe to be orthogonal to the optical axis of the illumination light, as shown in FIG. 10B. Shift to. Therefore, the intensity distribution changing unit 5 includes an optical element that is provided in one of the two light paths and changes the optical path length. Further, the intensity distribution changing unit 5 changes the pitch of the interference fringes by changing the wavelength of the laser beam, thereby changing the width Wd of the dark part. Therefore, for example, the laser light source 4f is a wavelength tunable laser light source, and the intensity distribution changing unit 5 includes a control element that controls the output wavelength of the laser light source 4f.

The illumination unit 4 in FIG. 10C forms a light and dark pattern on the surface B of the living tissue A like a shadow picture. The illumination unit 4 includes a light emitting unit 4 h and a mask 4 i provided at the distal end portion of the endoscope 2.
The light emitting unit 4h is a light source such as a xenon lamp, an LED (RGB), a white LED, or an infrared light source. The light emitting unit 4h may be an emission end of an optical fiber connected to a light source disposed outside the main body unit 3.

The mask 4i has a light-transmitting region that transmits white light and a light-blocking region that blocks white light, and a projection pattern corresponding to a light and dark pattern is formed from the light-transmitting region and the light-blocking region. The mask 4i is, for example, a light-shielding substrate having an opening as a light-transmitting region or a transparent substrate having a light-shielding film as a light-shielding region. The light output from the light emitting unit 4h is generated into the illumination light L having a bright and dark pattern by passing through the mask 4i.
Between the light emitting unit 4h and the mask 4i, a lens 4j for adjusting the divergence angle of the illumination light L applied to the living tissue A is disposed.

10C changes the intensity distribution over time by relatively moving the light emitting part 4h and the mask 4i in the width direction of the bright part and the dark part. Therefore, the intensity distribution changing unit 5 includes an actuator that moves at least one of the light emitting unit 4h and the mask 4i. Further, the intensity distribution changing unit 5 changes the pitch P of the light / dark pattern and the width Wd of the dark part by changing the distance between the light emitting part 4h and the mask 4i in the optical axis direction. Therefore, the intensity distribution changing unit 5 includes an actuator that moves at least one of the light emitting unit 4h and the mask 4i. The larger the distance between the light emitting part 4h and the mask 4i, the smaller the pitch P of the bright and dark pattern on the surface B of the living tissue A.

In the present embodiment, the intensity distribution changing unit 5 may continuously change the intensity distribution of the illumination light L between two light / dark patterns in which the light part and the dark part are mutually inverted.
When continuously changing the light / dark pattern, as shown in FIG. 11A, the imaging unit 6 performs shooting at three or more times at which the positions of the bright part and the dark part are different from each other, and the projection area of the bright part and You may acquire the 3 or more illumination image from which the position of the projection area of a dark part differs mutually. The separation processing unit 7 may create a surface layer image and a deep layer image from three or more illumination images. In this case, since three or more intensity values are obtained for the pixels at each position, the intensity values Is and Id are calculated using the maximum intensity value as Imax and the minimum intensity value as Imin.

As shown in FIG. 11B, when illuminating illumination light L having a sinusoidal light / dark pattern, Imax and Imax are obtained for each pixel using a phase shift method by capturing an illumination image under three or more appropriate conditions. Imin can be calculated.

In the present embodiment, the illuminating unit 4 causes the divergent light beam so that the light / dark pattern projected onto the surface B of the biological tissue A is enlarged in proportion to the imaging distance between the biological tissue A and the imaging unit 6. The illumination light L is preferably emitted toward the living tissue A.
With this configuration, simply by moving the endoscope 2 in the longitudinal direction with respect to the living tissue A, the light-dark pattern on the surface B of the living tissue A can be enlarged or reduced to change the width Wd of the dark part.

In the present embodiment, an imaging distance measuring unit that measures the imaging distance between the living tissue A and the imaging unit 6 is further provided, and the intensity distribution changing unit 5 is on the surface B of the living tissue A regardless of the imaging distance. The spatial period between the bright part and the dark part in the light / dark pattern is adjusted based on the shooting distance so that the spatial period (brightness / darkness pattern pitch P) between the bright part and the dark part is maintained constant. Also good.
By doing so, it is possible to create a deep image including information of a predetermined depth regardless of the shooting distance.

As the imaging distance measuring unit, any known means that can measure the imaging distance without contacting the living tissue A can be employed. When the light / dark pattern is a linear stripe pattern whose intensity changes sinusoidally as shown in FIG. 11B, the shooting distance measurement unit takes a picture from an illumination image acquired by the imaging unit 6 using the phase shift method. The distance can be calculated.

In the present embodiment, the illuminating unit 4 may illuminate the living tissue A with illumination light L composed of a plurality of lights having different wavelengths. For example, the illumination light L may be white light in which three lights of red, green, and blue are mixed.
When a plurality of lights having different wavelengths are used as the illumination light L, the intensity distribution of each light may be varied according to the wavelength so that the longer the wavelength, the smaller the period between the bright part and the dark part.

Generally, the light is more strongly scattered by the scatterer as the wavelength is shorter. Therefore, it is difficult for blue light to reach the deep layer D of the living tissue A compared to red light, and information included in the internally scattered light of blue light is information at a shallower position than the internally scattered light of red light. Therefore, the longer the wavelength, the shorter the period between the bright and dark parts, so that all the internal scattered light of red, green and blue has the same depth information and is included in the internal scattered light of each color. Can control the depth of information.

In the present embodiment, as shown in FIG. 12, a polarizer (polarization control unit) 9 that controls the polarization state of the illumination light L emitted from the illumination unit 4 and the living body tissue A enter the imaging unit 6. A polarizer (polarization selection unit) 10 that selects the polarization state of light may be further provided. The polarizer 9 and the polarizer 10 are provided at the tip of the endoscope 2, for example.
Specular light is generated on the surface B of the living tissue A by irradiation with the illumination light L. Specular light included in the first and second illumination images is separated into surface layer images. Therefore, the specular light affects the contrast of the surface layer image.

The specular light has the same polarization state as the illumination light L, and the surface scattered light and the internal scattered light do not have a specific polarization state. Therefore, by making the polarization direction of the polarizer 10 orthogonal to the polarization direction of the polarizer 9, the first and second illumination images that include the surface scattered light and the internal scattered light and do not include the specular light can be acquired. . Thereby, the contrast of the surface layer image based on the feature part E can be calculated without being affected by specular light, and the calculation accuracy of the depth information of the feature part E can be improved.

DESCRIPTION OF SYMBOLS 1 Endoscope system 2 Endoscope 3 Main body part 4 Illumination part 5 Intensity distribution change part 6 Imaging part 7 Separation processing part 8 Calculation part A Living tissue (Subject)
B Surface of biological tissue C Surface layer D Deep layer E Characteristic part Wd Width of dark part

Claims

An illumination unit that irradiates a subject with illumination light, and the illumination light has an intensity distribution in which a bright part and a dark part are spatially repeated in a light beam cross section perpendicular to the optical axis;
An intensity distribution changing unit that changes a width of the dark part in the intensity distribution of the illumination light;
An imaging unit that acquires a plurality of illumination images of the subject that are illuminated with illumination light having different widths of the dark part; and
A first separated image and a second separated image are created from each of the plurality of illumination images, and the first separated image includes more information about the depth of the subject than the second separated image. A processing unit;
An arithmetic unit that calculates depth information of the characteristic portion in the subject based on the plurality of first separated images and the plurality of second separated images created from the plurality of illumination images;
At least two of the intensity values of the pixels in the illumination image corresponding to each of the bright part, the dark part, and the part having the intensity between the bright part and the dark part of the intensity distribution. Creating the first and second separated images based on two intensity values;
An endoscope system in which the arithmetic unit calculates depth information of the feature based on a change between the plurality of first separated images and a change between the plurality of second separated images.
The illumination unit emits the illumination light as a divergent light beam so that the pattern of the bright part and the dark part on the subject is enlarged in proportion to the shooting distance between the imaging unit and the subject. The endoscope system according to claim 1.
A shooting distance measuring unit that measures a shooting distance between the imaging unit and the subject;
The intensity distribution changing unit is configured to change the intensity distribution in the intensity distribution based on the shooting distance so that the intensity distribution of the illumination light on the subject is constant regardless of the distance between the imaging unit and the subject. The endoscope system according to claim 1, wherein a cycle between the bright part and the dark part is changed.
The said illumination light consists of several light which has a mutually different wavelength, This several light has the said intensity distribution that the period of the said bright part and the said dark part becomes small, so that a wavelength is long. 4. The endoscope system according to any one of 3.
The endoscope system according to any one of claims 1 to 4, wherein the intensity distribution of the illumination light has a striped shape in which the bright portions and the dark portions of a band shape are alternately repeated in a width direction.
The endoscope system according to claim 5, wherein an intensity profile in the width direction of the bright part and the dark part of the intensity distribution of the illumination light has a substantially sinusoidal shape.
A polarization controller for controlling the polarization state of the illumination light;
The endoscope system according to claim 1, further comprising a polarization selection unit that selects a polarization state of light incident on the imaging unit from the subject.
The calculation unit is configured to obtain depth information of the feature based on a correspondence table in which a width of the dark part and a separation depth between the first separated image and the second separated image are associated with each other. The endoscope system according to any one of claims 1 to 7, which calculates
The calculation unit according to claim 8, wherein the calculation unit calculates a contrast of each of the plurality of sets of first and second separated images, and calculates depth information of the feature unit based on the contrast and the correspondence table. Endoscope system.